1. Field of the Invention
The present invention relates to motion estimation systems that estimate motion of a moving image, and more specifically to a method of extracting an image in the course of motion estimation.
2. Description of the Background Art
As the latest international standard for moving image coding, H.264 was developed and has been put to practical use by the VCEG (Video Coding Experts Group) of the ITU-T (International Telecommunication Union Telecommunication Standardization Sector), an international standardization organization for telecommunications, together with the ISO/IEC MPEG (Moving Picture Experts Group).
H.264 achieves compression twice as efficiently as MPEG-2 or MPEG-4 with the same image quality, and is fit for a wide range of uses from a videoconference at low bit rates to HDTV (High Definition TeleVision).
In an H.264 encoder, image data is transferred for motion estimation among a ME (Motion Estimation) system, a MC (Motion Compensation) system, and a frame memory. A memory capable of performing moving image compression efficiently with small frame memory capacitance is disclosed in Japanese Patent Application Laid-Open No. 2004-222262, for example.
In Japanese Patent Application Laid-Open No. 2004-222262, improvements are made mainly to a frame memory, and not to an internal memory used in a motion estimation system. Thus high-speed motion estimation cannot be performed with a motion estimation system having a relatively simple circuit structure.